1. Technical Field
The present invention generally relates to improvement of microwave motion sensing technology for motion detection, intrusion detection and occupancy detection, more particularly, to devices equipped with a microwave motion sensing capacity for uses in home automation including but not limited to lighting and security management.
2. Description of Related Art
The detection zone of a passive infrared ray (PIR) sensor disposed in a security light fixture for instance is defined and limited by the angle coverage of its detection lens. Once the detection lens is designed and constructed the space coverage of its detection zone is pretty much defined and the only thing adjustable is just the angle of detection lens and consequently the direction of the detection zone. If a much wider detection coverage is required, for instance 270 degree or even 360 degree horizontal space, two or three PIRs need to be integrated. Additionally if vertical space needs detection then additional PIR (3rd or 4th PIR) may need to be considered. The need to install the detection lens outside of the security light fixture also limits the capacity of artistic design of the lighting arts.
On the other hand, the microwave motion sensor could detect motion signals coming from all different directions without being disrupted by any non-metallic obstacles such as wall, buildings, tree, etc. The penetration makes it possible to install and hide the microwave motion sensor inside the glass or plastic diffuser to improve the artistic design of the lighting arts. The omnidirectional detecting capacity makes the microwave motion sensor a more useful detection device under certain conditions.
However, the high penetration and the spreading capacity of microwave signal are actually untamable when it comes to home lighting application. While the microwave detection method has dual advantages in terms of being able to hide the microwave motion sensor 90 inside the lighting fixture and its detecting capacity is unrestricted by direction or angle of intruding motion. The high penetrating and spreading capacity could easily cause problems for the users in that the light may be unexpectedly activated by the body motion in the next door or neighboring rooms.
Please refer to FIG. 1A, which schematically illustrates a prior art illumination apparatus 9 with a microwave motion sensor 90. The prior art illumination apparatus 9 is composed of a microwave motion sensor 90, an illumination module 92, a mounting module 94 and a light diffuser 96. The prior art microwave motion sensor 90 is composed of a circuit assembly which emits microwave signals and receives echoed microwave signals returning from any moving object(s) in a three dimensional (3D) spherical detection zone. The radius of such three dimensional spherical detection zone is determined by the power level set for the whole circuit assembly.
However, the microwave signal is able to penetrate through any non-metallic barriers, the prior art microwave motion sensor 90 may detect the motions occurring in the neighborhood such as next doors, upstairs or downstairs and consequently the illumination module 92 is unexpectedly turned on. The dotted lines as shown in FIG. 1B represent the detection zone of a 3 dimension spherical space that the microwave sensing unit 90 is able to detect and activate the lighting device to turn on. The wall or ceiling penetration effect is an obvious problem. Although it could be managed to reduce the power of the microwave signals so that the radius of the 3D spherical detection zone is confined to a smaller spherical space to avoid the wall penetration problem. However, it will limit the application of such microwave motion sensor 90.
In addition, please refer to FIGS. 1C, 1D and 1E, U.S. Pat. No. 8,169,356 B2 disclosed a method and apparatus using microwave motion sensors having a reflector 40 for enhanced lookdown ability; the prior art was invented for improving the lookdown detection capacity for a security alarm system. The reflector 40 of said prior art was designed to be positioned far above the microwave radiating elements 30 of the microwave motion sensor therefore the reflector 40 is merely invented for enhancing the lookdown ability to detect the motion intrusion in the lookdown area under the reflector 40. The reflector 40 with a curved shape so designed has no control over the microwave signal transmitting to all other directions except the conic sheltered area SA above the reflector 40.
The distance or the relative position between the bottom piece of microwave radiating elements 30 and the reflector 40 determines the scope of conic sheltered area SA. The sheltered area SA is the cross line space of FIG. 1C above the reflector 40, wherein the microwave signal is banned for detection. In other words, the prior art is an open space detecting device that can detect any motion intrusion from all directions except the limited upper zone sheltered by the reflector 40. As shown in FIGS. 1D and 1E which is cited from the FIG. 1C of the prior art, U.S. Pat. No. 8,169,356 B2, the lowest position of the microwave radiating elements 30 determines the scope of the sheltered area SA (as cross line area in FIG. 1C) above the reflector 40.
The prior art security alarm device with microwave motion sensors is able to detect any motion intrusion occurred in the open space outside the sheltered area SA. In other words, when the security alarm device is used for outdoor application, a bird flying across the upper space outside of the sheltered area SA or a motion from adjacent neighbor may easily trigger the microwave motion sensor to activate the security alarm. Furthermore, when the said security alarm device is applied for indoor application, a motion from next door or upper/lower floor may also trigger the microwave motion sensor to unexpectedly activate the security alarm. In either case, the non-managed microwave detection capacity could create more embarrassment than necessary. It might be the intention of the prior art to use the reflector 40 to enhance the downward microwave signal while using lower level power microwave radiation to reduce the detection range for non-downward space so as to avoid the embarrassment of unnecessary triggering.